How to use a DMM, Digital Multi Meter

Summary

In this video, John from The Machine Shop explains the features and uses of digital multimeters (DMMs) for analyzing electrical circuits. He covers both manual and auto-ranging DMMs, demonstrating how to measure voltage, resistance, capacitance, and current. John also shows practical applications by testing components like capacitors and diodes, troubleshooting a circuit, and measuring current draw from a motor. The video offers viewers a detailed, hands-on guide to effectively using a DMM for circuit analysis, with tips on ensuring accurate readings and diagnosing problems in electrical setups.

Takeaways

• 😀 Digital multimeters (DMMs) are essential tools for measuring various electrical signals, such as voltage, resistance, and current.
• 😀 DMMs feature a digital display, typically an LCD, to show measurements.
• 😀 There are two types of DMMs: manual ranging and auto ranging. Manual requires the user to select the appropriate range, while auto-ranging adjusts the range automatically.
• 😀 The Fluke 175 is an example of an auto-ranging DMM that can measure voltage, resistance, current, capacitance, diodes, and more.
• 😀 Continuity testing is a key feature of DMMs, allowing users to check if there is a connection between two points, accompanied by an audible beep.
• 😀 DMM leads are commonly color-coded, with black for common (ground) and red for voltage or current measurements.
• 😀 Specialized probes such as sharp-pointed probes and crocodile clips can be used for more precise or hands-free measurements in tight spaces.
• 😀 When measuring voltages, always ensure the DMM is set to the correct voltage range (DC or AC) based on the circuit being tested.
• 😀 Capacitor and diode testing modes allow users to test components in a circuit, verifying their functionality (e.g., a capacitor’s capacitance or a diode’s forward voltage).
• 😀 To measure current, the DMM’s lead needs to be moved to the current input, and the circuit must be adjusted to allow for current measurement.
• 😀 Using the min/max feature on the DMM helps track current changes under stress conditions, allowing users to see peak values.
• 😀 Proper safety practices should be followed, especially when measuring high-voltage circuits, to avoid electrical hazards.

Q & A

What is a Digital Multimeter (DMM)?

A Digital Multimeter (DMM) is a tool used to measure different electrical values such as voltage, resistance, current, capacitance, and continuity, typically displayed on a digital screen.

What is the difference between manual ranging and auto-ranging DMMs?

A manual ranging DMM requires the user to select the measurement range, such as voltage or resistance. An auto-ranging DMM automatically detects the optimal range for the measurement, simplifying the process.

What are the primary components or features of a DMM?

A DMM typically includes an LCD display, measurement settings for voltage, resistance, current, capacitance, and diode testing, as well as probes for connecting to electrical circuits.

What is the purpose of continuity testing in a DMM?

Continuity testing allows the DMM to check if there is a complete electrical connection between two points. It provides an audible sound and visual reading (ohms) when a connection is detected.

Why is it important to use the correct range when measuring voltage with a manual ranging DMM?

Using the correct range ensures accurate readings. If the range is too large or too small for the measurement, the DMM may provide incorrect or unreliable results.

How can a DMM be used to test a battery's charge?

A DMM can measure the voltage of a battery by setting it to DC voltage mode. By connecting the probes to the battery's terminals, you can check if the voltage matches the expected value, indicating the charge level.

What is the significance of testing components like capacitors and diodes with a DMM?

Testing capacitors and diodes ensures they are functioning correctly in a circuit. A DMM in capacitance mode can measure the capacitance of a capacitor, while diode testing mode checks if the diode is working properly by measuring voltage drop.

How do you measure current in a circuit using a DMM?

To measure current, you need to interrupt the circuit and insert the DMM probes in series with the load. You also need to ensure the DMM is set to the appropriate current mode (DC or AC) and that the probes are connected to the correct ports.

What is the importance of measuring both input and output current in a circuit?

Measuring both input and output current helps determine if the circuit is drawing the expected amount of power and if it is operating efficiently. This can reveal issues like overcurrent or power loss in the system.

How does the 'Min Max' function on a DMM help in testing circuits?

The 'Min Max' function allows you to capture the minimum and maximum readings of voltage or current during tests, which helps analyze fluctuations or identify issues like spikes or drops in the circuit's performance.